Adjustable safety latch



April 18, A AMESv ADJUSTABLE SAFETY LATCH 2 Sheets-Sheet l Fi led March 5, 1965 INVENTOR.

William A. Ames Attorney April 18, W A AMES ADJUSTABLE SAFETY LATCH 2 Sheets-Sheet 2 Filed March 5, 1965 INVENTOR. William A. Ames United States Patent Office 3,314,702 ADJUSTABLE SAFETY LATCH William A. Ames, 834 Pear Ave., Sunnyvale, Calif. 94087 Filed Mar. 3, 1965, Ser. No. 436,884 5 Claims. (Cl. 292-469) This invention relates to latches for use on doors, drawers, cabinets, cupboards, and the like which readily permit opening by adults but prevent opening by children or those in a weakened condition. My invention is especially suited for preventing access to closets or storage spaces by children while permitting ready access by adults. It is especially useful for eliminating the need for keys and providing other flexibility, as brought out more fully below.

Previous devices which have been constructed to accomplish this purpose have relied on various mechanisms which required a predetermined amount of excess force or torque to operate the latch mechanism which was of a high order of magnitude so that only strong adults could operate it. This excessive force which was required was of a constant, predetermined magnitude and latches so constructed were not capable of being operated also in a normal manner using a normal amount of force during times when the safety feature was not required. In many of the previous latches of this class also the amount of force required to operate the latch was so great that only an adult male was able to do so and in a family this would mean only the husband could operate the latch. This, of course, kept the children out but also frequently kept out the weaker wife which, of course, was an undesirable situation.

All previous latches of this class also had another serious disadvantage. Whenever the nature or occupancy of the area or compartment sought to be protected from access changed so that the above safety feature was not only no longer necessary but undesirable, it was necessary to replace the entire latch mechanism to one of a conventional type easily opened from both sides by anyone. This occurred frequently in modern homes in which very often a multiplicity of storage cabinets are located side by side as in a modern kitchen for example. Here it is desirable that all latches have the same appearance but perhaps only a few of them should be arranged so that children could not open them. The number of the latter will vary from time to time and the use of the previous latches of this class would make it necessary to remove and replace latches as frequently as the conditions changed which was highly impracticable.

In some of the previous mechanisms employed moreover, the greater force required to open the latch was accompanied by an equal amount of greater force required to close it, thus preventing the ready slamming shut of a door which is equipped with a latch of that type, the latter being a very highly desirable feature under some conditions.

Another disadvantage of many previous latches of this type was that they ofen required a heavy pushing action against the knob to engage the latch while the door itself was so hung as to require a pulling action to open. The would be especially true of doors on storage cabinets, making such latches very inconvenient and clumsy to use.

Finally, all of the latches which have heretofore been constructed to accomplish the same ultimate objective of safety as does my invention are large, often clumsy, complicated, and of poor general appearance. In all cases the latch embodying the safety features was much different in appearance than conventional latches which,

3,314,702 Patented Apr. 18, 1967 of course, is undesirable where there is a large number of these side by side.

It is therefore a primary object of my invention to provide a safety latch of the class described in which the force necessary to open the latch would be adjustable.

It is still another object of my invention to provide a safety latch of the class described which may be readily converted to operate using a normal amount of force.

It is yet another object of my invention to provide a safety latch of the class described which would permit easy slamming shut of the door even when the mechanism was adjusted for maximum opening force.

I t is a further very important object of my invention to provide a safety latch of the class described which would be much simpler, more effective, and more efficient to operate and maintain.

It is a further object of my invention to provide a safety latch of the class described which would have the outward appearance of any conventional latch.

I have discovered that by utilizing a latch mechanism of the axial push button or plunger release type combined with a spring having an adjustable amount of tension provided for in combination with the novel features and construction of the rest of my mechanism I am able to accomplish all of the foregoing objects, as well as provide other advantages which will be apparent from a study of the description which follows and the accompanying drawings which form a part of this specification, in which:

FIG. 1 is a longitudinal sect-ion through a preferred embodiment of my invention shown applied to a swinging door and frame in the closed position.

FIG. 2 is an exploded perspective view of the important components of the embodiment of FIG. 1 illustrating their relation to one another and method of assembly.

FIG. 3 is an alternate embodiment of my invention, also shown in longitudinal section in the closed position on a door and frame.

FIG. 4 is a plan view of the important components of FIG. 3.

Referring now to the figures and particularly to FIG. 1 and FIG. 2, there is seen a knurled turning knob 1 which is rotatably secured to the outside of swinging door 16 by means of recessed collar 1a. The knob 1 is equipped with a concentric threaded hole 112 and a set screw is for locking onto cam shaft 2b. The shaft 2b is integral with a double lobed cam 2 having diametrically opposite spaced holes 2a. The threaded section 20 engages with the threaded section 1b of the knob previously described.

The reciprocating plunger 3 carrying an integral head 3a is slidably positioned in a concentric hole in the center of cam shaft 2b as shown. The sliding latch frame 5, whose construction is best seen on FIG. 2, is generally forked shaped with two L-shaped prongs and carries latch member Set as an integral part. Locking sleeve 6 equipped with two locking prongs 6a is positioned so as to be intermittently engaged with the locking holes 2a in cam 2. A light duty spring 7 which is always under a light amount of tension is positioned between a ridge in locking sleeve 6 and the inside of the inner half-casing 9.

Pressure bar 8b is positioned between the opposite faces of cam 2 and plunger head 3a and in light sliding frictional relation with the surfaces. This bar is equipped with holes 8a to permit passage of locking prongs 6a. It is held in position by pressure bar housing 8 which in turn is fixedly mounted on the inner surface of casing 9.

A heavy duty spring 10 which is capable of being placed under a relatively high degree of tension is concentrically positioned inside of locking sleeve 6 and hous- 3 ing 11. Housing 11 has a threaded section 11a arranged to receive a threaded section 12a of knurled adjusting screw 12. Housing 11 is further equipped with a flange section 11b through which it may be fixedly positioned on the inside of casing 9 by any suitable means, such as spot welding.

A thrust washer 13 serves to provide sliding frictional surfaces for one face of cam 2 and the interior surface of outer half-casing 4. Casing 4 is secured to the inside of swinging door 16 in any suitable manner, not shown. The door 16 is shown being held in a closed position against frame 17 by latch 5a.

Operation The operation of my invention is as follows. When the locking prongs 6a are engaged in locking holes 2a it is evident that cam 2 is prevented from being turned by means of knob 1 and the entire mechanism is in a positively locked position.

When it is desired to open the latch, plunger 3 is pressed inward and the combined action of plunger head 3a and locking sleeve 6 against the tension of springs 7 or 10 or both, as will be explained later, causes the locking prongs 6a to move out from the locking holes 2a of cam 2. Rotation of knob 1 in either direction will then cause either of the two lobes of cam 2, which are positioned diametrically opposite as shown, to push against the L-sha-ped end of sliding latch frame 5 imparting a motion of translation. This causes latch 5a to move out of engagement with frame 17 against the action of spring 14 and spring stop 15. The door may then be opened. When opened and knob 1 let go of, latch So will spring back by the action of spring 14. To close it, it is then merely necessary to slam the door and the latch will spring closed since its operation in this respect is independent of cam 2 which has returned to its locked position with the removal of the pressure from the plunger 3. The latch is now again in a positively locked position.

In order to make it difficult to open the latch, knurled screw 12 is screwed down against heavy duty spring 10 to any degree desired. The amount of force necessary to depress plunger 3 and hence to operate the latch, may thus be adjusted to suit the strength of the weakest person who is to be permitted access to the space behind the door which in this case may be the mother of the family, but still make it impossible for the small children to open.

If the safety feature is no longer desired or not desired on this particular door, then knurled screw 12 is slacked ofi completely and light duty spring 7 takes over. This spring is under such tension that it requires very little pressure on plunger 3 to unlock the cam and operate the latch. It is thus seen how not only an adjustable amount of force is built in my device as a safety factor, but the device may be used and operated without such safety factor when desired. Also it is apparent that in appearance from the outside, my device is exactly like that of any similar latch mechanism.

It is also evident from the foregoing that no set pressure need be exerted against the door at all. For example, plunger 3 may be pressed in by the thumb and this force balanced by the action of the first and second fingers behind knob 1 which are in eifect pulling on the door in order to open it after the latch 50 has been released. This overcomes the necessity for pushing and pulling on the door at the same time which is made necessary by many existing devices.

An alternate embodiment which while not possessing the degree of flexibility and some of the other advantages shown in FIGS. 1 and 2, is shown on FIGS. 3 and 4. Here I have sacrificed some of the flexibility in the interest of simplicity and cheapness of construction, while not departing from the basic principles of my invention. In FIGS. 3 and 4 insofar as this embodiment corresponds to that of FIGS. 1 and 2, like parts bear like numbers plus 100. Thus knob 101 is positioned on cam shaft 10% through threaded section 10112 and rides on recessed collar 101a positioned on door 116. Cam 102, which is generally triangular in shape in this embodiment, rides against sliding latch frame which in this embodiment is of L-shaped slotted construction and carries latch 105a. This embodiment employs a locking member 166 which is capable of being moved back and forth on cam shaft 102!) by the action of reciprocating plunger 103 working against the tension of spring 110. It is evident that this locking member serves to positively hold latch frame 104 in a locked position until depressed by the action of plunger 103. Latch spring 114 and latch spring stop serve latch 105a in a manner similar to that in the previous embodiment. Washer casing 104, shaped and spaced as shown. The adjustable force required to operate the latch is obtained by adjusting the tension in spring 114 by knurled adjusting screw 112.

Other embodiments will now become evident to those skilled in the art and I do not limit myself to those here shown except as I do so in the claims which follow.

I claim:

1. A door latch operating mechanism comprising:

a rotatable knob fixedly positioned upon a rotating shaft having a concentric axial hole therethrough;

a cam fixedly positioned on said shaft;

positive locking pins engaging said cam;

a first relatively strong spring for urging said locking pins to an engaged position with said cam;

a second relatively weak spring for urging said locking pins to an engaged position with said cam;

an adjusting screw engaging said first spring and disposed to adjust the tension thereon to a predetermined value;

said adjusting screw being further disposed to remove all tension on said first spring thereby transferring it to said second spring;

a reciprocating plunger concentrically mounted through said hole in said shaft and positioned to disengage said locking pins from said cam;

a cam follower positioned in reciprocating relation to said cam;

a latch positioned on said cam follower;

a spring disposed to urge said follower against said cam.

2. A door latch operating mechanism comprising:

a rotatable knob fixedly positioned upon a rotating shaft having a concentric axial hole therethrough;

a cam fixedly positioned on said shaft;

a cam follower positioned in reciprocating relation to said cam and fixedly positioned on a sliding latch;

a first spring for urging said follower against said cam;

a reciprocating plunger concentrically mounted through said hole in said shaft;

a key fixedly positioned on said plunger and arranged to engage and disengage said latch upon movement of said plunger;

a second spring for urging said key to an engaged position with said latch;

an adjusting screw engaging said second spring and disposed to adjust the tension thereon to a predetermined value.

3. In a rotating cam operated the improvement comprising:

a knob disposed to rotate said cam;

positive locking pins for engaging said cam and holding said latch in a locked position;

a spring disposed to hold said pins in a normally locked position;

independent means for disengaging said locking pins from said cam by the application of a predetermined amount of pressure alone against said locking pins;

an adjustable screw pressure;

door latch mechanism disposed to vary said predetermined 113 may be an integral part of v posed to operate without the application of any pressure against said door.

4. The latch mechanism of claim 1 in which said follower and said latch are capable of reciprocating movement independent of the rotation of said cam thereby permitting said latch to be forced into an open position by slamming said door while said locking means engages said cam.

5. The latch mechanism of claim 2 in which said cam is disposed to move said latch into a closed position only, and said first spring is disposed to release said latch to an open position upon depression of said reciprocating plunger.

References Cited by the Examiner UNITED STATES PATENTS Schlage 292l69 Schlage.

Karczewski 292-169 Voight 292169 Hopgood 292169 Collier 292-169 Wright 292336.3 Keeler 292-336.3

MARVIN A. CHAMPION, Primary Examiner. J. R. MOSES, Assistant Examiner. 

1. A DOOR LATCH OPERATING MECHANISM COMPRISING: A ROTATABLE KNOB FIXEDLY POSITIONED UPON A ROTATING SHAFT HAVING A CONCENTRIC AXIAL HOLE THERETHROUGH; A CAM FIXEDLY POSITIONED ON SAID SHAFT; POSITIVE LOCKING PINS ENGAGING SAID CAM; A FIRST RELATIVELY STRONG SPRING FOR URGING SAID LOCKING PINS TO AN ENGAGED POSITION WITH SAID CAM; A SECOND RELATIVELY WEAK SPRING FOR URGING SAID LOCKING PINS TO AN ENGAGED POSITION WITH SAID CAM; AN ADJUSTING SCREW ENGAGING SAID FIRST SPRING AND DISPOSED TO ADJUST THE TENSION THEREON TO A PREDETERMINE VALUE; SAID ADJUSTING SCREW BEING FURTHER DISPOSED TO REMOVE ALL TENSION ON SAID FIRST SPRING THEREBY TRANSFERRING IT TO SAID SECOND SPRING; A RECIPROCATING PLUNGER CONCENTRICALLY MOUNTED THROUGH SAID HOLE IN SAID SHAFT AND POSITIONED TO DISENGAGE SAID LOCKING PINS FROM SAID CAM; A CAM FOLLOWER POSITIONED IN RECIPROCATING RELATION TO SAID CAM; A LATCH POSITIONED ON SAID CAM FOLLOWER; A SPRING DISPOSED TO URGE SAID FOLLOWER AGAINST SAID CAM. 